Theoretical approaches are being developed to extract information concerning the nature of internal motions in a variety of biopolmers from nuclear magnetic relaxation and time-resolved fluorescence depolarization experiments. The unique information content of NMR relaxation experiments on macromolecules has been established and a model-free approach to obtain that information has been proposed and extensively applied. A theory required to analyze solid state spin-lattice relaxation times has been developed. Contact has been made between molecular dynamics simulations and fluorescence depolarization of tyrosines in proteins. In addition, the role of diffusion in ligand binding to macromolecules and cell-bound receptors, where there is competition between reactive sites, has been analyzed. Finally, the theory of the chronoamperometric current to microelectrodes has been worked out.